Score as many times as you can before the time is up! As you progress in the game, you'll have to score more times to pass to the next level. If you score consecutively you earn bonus points, with a multiplicative effect as you do it more times. If you score 3 red baskets you'll earn 1000 points, and for 3 blue ones you earn 5 seconds of extra time.
Use the space bar to aim (when you're closer to the central indicators, more chances you have to score).